fix: make express parse body

src/plugin.ts

@@ -15,6 +15,7 @@
 
 import {Converter} from '@openstapps/core-tools/lib/schema';
 import {Logger} from '@openstapps/logger';
+import bodyParser from 'body-parser';
 import express from 'express';
 import * as http from 'http';
 import * as http2 from 'http2';
@@ -119,6 +120,7 @@ export abstract class Plugin {
               responseName: string,
               version: string) {
 
+    this.app.use(bodyParser.json());
     this.port = Plugin.normalizePort(
       /* istanbul ignore next */
       typeof process.env.PORT !== 'undefined' ? process.env.PORT : port.toString());